Add discardable memory emulation for non-android/mac platforms

base/memory/discardable_memory_mac.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/discardable_memory.h"
 
 #include <mach/mach.h>
 #include <sys/mman.h>
 
 #include "base/basictypes.h"
@@ skipping 57 matching lines @@
  private:
   void* const memory_;
   const size_t size_;
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryMac);
 };
 
 }  // namespace
 
 // static
-bool DiscardableMemory::Supported() {
+bool DiscardableMemory::SupportedNatively() {
   return true;
 }
 
 // static
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemory(
     size_t size) {
   vm_address_t buffer = 0;
   kern_return_t ret = vm_allocate(mach_task_self(),
                                   &buffer,
                                   size,
@@ skipping 13 matching lines @@
   return true;
 }
 
 // static
 void DiscardableMemory::PurgeForTesting() {
   int state = 0;
   vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
 }
 
 }  // namespace base